Centerless grinder having inside diameter size control and method therefor

Abstract

A centerless grinding machine comprises a stationary disk, a following disk, and a shoe, which cooperate to hold and rotate a workpiece. The following disk is mechanically loaded to the bias towards the stationary disk and the shoe so that the workpiece is secured between an outer circumference of the disks and the shoe. A diameter detector detects an outside diameter of the workpiece by detecting a displacement of the following disk by the workpiece. From this information, a controller controls an X-Z grinder to grind an inner surface of the workpiece. This grinding is in response to the outside detector detected by the diameter detector. As a result, the inner diameter can be machines to closer tolerances than are available in the outer diameter.

We claim: 
     
       1. A method for controlling a grinding machine including a disk for rotating a workpiece, a shoe for cooperating with the disk and a workpiece support element to hold the workpiece, and a grinder for grinding an inner surface of the workpiece during the rotation, the method comprising: determining an outside diameter of the workpiece by detecting displacement of the disk;   calculating a necessary wall thickness that will yield the desired inner diameter; and   operating the grinder to remove material along the inner surfaces of the workpiece to achieve the calculated wall thickness.   
     
     
       2. The method of claim 1 further comprising mechanically loading the disk to maintain engagement with the workpiece so that the workpiece is secured between an outer circumference of the disk, the shoe, and the workpiece support element. 
     
     
       3. The method of claim 1 further comprising sensing the displacement of the disk to determine the outside diameter. 
     
     
       4. The method of claim 1 further comprising providing a workpiece support element including a second disk for cooperating with the disk and the shoe to hold the workpiece. 
     
     
       5. A centerless grinding machine comprising: a disk for rotating a workpiece having an outside surface and an inner surface;   a workpiece support element;   a shoe for cooperating with the disk and the workpiece support element to hold the workpiece;   a diameter detector that detects the outside surface of the workpiece and generates a detector signal;   a grinder that grinds the inner surface of the workpiece during rotation; and   a controller that receives the detector signal and determines a wall thickness such that the grinder engages and grinds the inner surface in response to the detector signal from the diameter detector to provide a selected internal diameter of the workpiece.   
     
     
       6. The centerless grinding machine of claim 5, wherein the disk is mechanically loaded to maintain engagement with the workpiece so that the workpiece is secured between an outer circumference of the disk, the shoe, and the workpiece support element. 
     
     
       7. The centerless grinding machine of claim 6, wherein the diameter detector detects the outside diameter by sensing the displacement of the disk. 
     
     
       8. The centerless grinding machine of claim 5, wherein the controller controls the grinder to machine the inner surface of the workpiece to achieve a desired wall thickness which is determined in response to the outside diameter detected by the diameter detector. 
     
     
       9. The centerless grinding machine of claim 5, wherein the workpiece support element is another disk cooperating with the disk and the shoe to hold the workpiece. 
     
     
       10. The centerless grinding machine of claim 5, wherein the grinder comprises: a grinding head;   a z-stage for plunging the grinding head into the workpiece; and   an x-stage for bringing the grinding head into engagement with the inner surface of the workpiece.   
     
     
       11. A centerless grinding machine comprising: a first disk that supports a workpiece having an outer surface and a grinding surface;   a following disk;   a shoe positioned relative to the first disk and the following disk, the shoe cooperating with the first disk and the following disk to hold and rotate the workpiece;   a diameter detector that detects the outside surface of the workpiece by detecting a displacement of the following disk by the workpiece, the detector generating a detector signal;   a grinder that grinds the grinding surface of the workpiece; and   a controller electrically connected to the detector and the grinder that controls the grinder in response to the detector signal generated by the diameter detector.   
     
     
       12. The centerless grinding machine of claim 11, wherein the following disk is mechanically loaded to the bias towards the stationary disk and the shoe. 
     
     
       13. The centerless grinding machine of claim 11, wherein the controller controls the grinder to machine the inner surface of the workpiece to achieve a desired wall thickness which is determined in response to the outside diameter detected by the diameter detector. 
     
     
       14. The centerless grinding machine of claim 13, wherein the grinder comprises: a grinding head;   a z-stage for plunging the grinding head into the workpiece; and   an x-stage for bringing the grinding head into engagement with the inner surface of the workpiece.   
     
     
       15. A centerless grinding machine comprising: a first stationary workpiece support element, a second stationary workpiece support element, and a following workpiece support element adapted to cooperate to hold and rotate a workpiece;   a diameter detector that detects an outside surface of the workpiece by detecting displacement of the following workpiece support element by the workpiece, the detector generating a measurement signal representative of the detected surface;   a grinder for grinding an inner surface of the workpiece during the rotation; and   a controller electrically connected to the grinder to control grinding of the inner surface in response to the measurement signal received by the controller from the diameter detector such that the workpiece has a selected wall thickness.   
     
     
       16. The centerless grinding machine of claim 15, wherein the first and second stationary workpiece support elements are a stationary disk and a shoe, respectively. 
     
     
       17. The centerless grinding machine of claim 15, wherein the following workpiece support element is a following disk. 
     
     
       18. The centerless grinding machine of claim 15, wherein the following workpiece support element is mechanically loaded to maintain engagement with the workpiece so that the workpiece is secured between the first stationary workpiece support element, the second stationary workpiece support element, and the following workpiece support element. 
     
     
       19. The centerless grinding machine of claim 15, wherein the controller controls the grinder to machine the inner surface of the workpiece to achieve a desired wall thickness which is determined in response to the outside diameter detected by the diameter detector. 
     
     
       20. The centerless grinding machine of claim 15, wherein the grinder comprises: a grinding head;   a motor for rotating the grinding head;   a z-stage for plunging the grinding head into the workpiece; and   an x-stage for bringing the grinding head into engagement with the inner surface of the workpiece.